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Biomedical subjects

J S Wright

Publications and source records attributed to J S Wright.

At least 19 recordsLinked to original sources
PubMed2001

Predicting the activity of phenolic antioxidants: theoretical method, analysis of substituent effects, and application to major families of antioxidants.

A procedure based on density functional theory is used for the calculation of the gas-phase bond dissociation enthalpy (BDE) and ionization potential for molecules belonging to the class of phenolic antioxidants. We show that use of locally dense basis sets (LDBS) vs full basis sets gives very similar results for monosubstituted phenols, and that the LDBS procedure gives good agreement with the change in experimental BDE values for highly substituted phenols in benzene solvent. Procedures for estimating the O--H BDE based on group additivity rules are given and tested. Several interesting classes of phenolic antioxidants are studied with these methods, including commercial antioxidants used as food additives, compounds related to Vitamin E, flavonoids in tea, aminophenols, stilbenes related to resveratrol, and sterically hindered phenols. On the basis of these results we are able to interpret relative rates for the reaction of antioxidants with free radicals, including a comparison of both H-atom-transfer and single-electron-transfer mechanisms, and conclude that in most cases H-atom transfer will be dominant.

Antioxidants↗
PubMed2001

The phosphoryl transfer domain of UhpB interacts with the response regulator UhpA.

Bacterial two-component regulatory systems control the expression of target genes through regulated changes in protein phosphorylation. Signal reception alters the ability of a membrane-bound histidine kinase (HK) protein to transfer phosphate from ATP to a highly conserved histidine residue. The transfer of phosphate from the histidine to an aspartate residue on the cognate response regulator (RR) changes the ability of the latter protein to bind to target DNA sequences and to alter gene transcription. UhpB is the HK protein which controls production of the sugar phosphate transporter UhpT. Elevated expression of full-length UhpB or of a soluble hybrid protein, GST-Bc, which is glutathione S-transferase (GST) fused to the cytoplasmic C-terminal portion of UhpB, results in complete blockage of uhpT expression in a uhp(+) strain. This dominant-negative interference could result from the ability of GST-Bc to bind and sequester the RR UhpA and to accelerate its dephosphorylation. The portion of GST-Bc responsible for the interference phenotype was localized using truncation, linker insertion, and point mutations to the region between residues 293 and 366 flanking His-313, the putative site of autophosphorylation. Point mutations which allow GST-Bc to activate uhpT expression or which relieve the interference phenotype were obtained at numerous sites throughout this region. This region of UhpB is related to the phosphoryl transfer domain of EnvZ, which forms half of an interdimer four-helix bundle and is responsible for dimerization of its cytoplasmic domain. The expression of GST fusion proteins carrying the corresponding portions of EnvZ strongly interfered with the activation of porin gene expression by OmpR. The GST-Bc protein accelerated dephosphorylation of P-UhpA. Reverse transfer of phosphate from P-UhpA to GST-Bc was observed in the presence of the metal chelator EDTA and depended on the presence of His-313. Phosphate transfer from P-UhpA to the liberated phosphoryl transfer domain also occurred. Taken together, these results indicate that the phosphoryl transfer-dimerization domain of UhpB participates in the specific binding of UhpA, in the control of autokinase activity, and in the dephosphorylation of P-UhpA.

Amino Acid Sequence↗
PubMed2000

Hemiketal formation of dehydroascorbic acid drives ascorbyl radical anion disproportionation.

In this paper the relationship between the ascorbate anion (AH(-)) and its oxidation products, ascorbyl radical anion (A&z.rad;(-)) and dehydroascorbic acid (DHA), are studied by means of theoretical calculations. Additional calculations are performed on alpha-hydroxytetronate, a model compound of ascorbate lacking the side chain. The method uses density functional theory with the B3LYP functional and a polarizable conductor dielectric model to compute solvation effects. Our results indicate that the model compound reacts with the alpha-tocopheroxyl radical to regenerate vitamin E with a free energy change of reaction (in water) of -7.4 kcal/mol. This reaction is 2.9 kcal/mol more exergonic than the corresponding reaction involving ascorbate, suggesting that the model compound may make a more effective antioxidant than ascorbate. However, the disproportionation of the ascorbyl radical anion, a reaction that regenerates AH(-), is found to be exergonic while the similar reaction involving the model compound is slightly endergonic. The reason for the difference is that the disproportionation of A&z. rad;(-) is found to be driven by the formation of the hemiketal structure of dehydroascorbic acid (DHA).

Ascorbic Acid↗
PubMed2000

Vulnerability to noise-induced hearing loss in 'middle-aged' and young adult mice: a dose-response approach in CBA, C57BL, and BALB inbred strains.

Vulnerability of the cochlea to noise-induced permanent threshold shifts (NIPTS) was examined in young adult (1-2 months) and 'middle-aged' (5-7 months) CBA/CaJ, C57BL/6J, and BALB/cJ inbred mice. For each age and strain, a dose-response paradigm was applied, whereby groups of up to 12 animals were exposed to intense broadband noise (110 dB SPL) for varying durations. Exposure durations reliably associated with <10% and >90% probability of a criterion amount of NIPTS (determined 2 weeks post-exposure) were identified, and the minimum NIPTS exposure and the slope of the dose-response relation were then derived by numerical modeling. For all three strains, young adult mice were more susceptible to NIPTS than older adults; That is, a shorter exposure was able to cause NIPTS in the younger mice. Strain comparisons revealed that C57 mice were more susceptible than CBAs in the older age group only. At both ages examined, however, BALB mice were most susceptible to NIPTS. When animals with a similar amount of NIPTS were compared, outer hair cell loss in the cochlear base was more widespread in the younger animals. BALB mice appear particularly susceptible to noise-induced outer hair cell loss throughout life. Our data suggest that the mechanism or site of noise injury differs between young adults and older adults, and may depend on genetic background. The finding that both BALB and C57 mice, which show pronounced age-related hearing loss, are also especially vulnerable to noise supports the notion that genes associated with age-related hearing loss often act by rendering the cochlea susceptible to insults.

Aging↗
PubMed2000

The histidine kinase domain of UhpB inhibits UhpA action at the Escherichia coli uhpT promoter.

The histidine kinase (HK) component of many two-component regulatory systems exhibits regulated ability to phosphorylate itself and to participate in transfer of phosphate to and from its cognate response regulator. The signaling system that controls expression of the UhpT sugar phosphate transporter in Escherichia coli in response to external glucose 6-phosphate includes the HK protein UhpB and the polytopic membrane protein UhpC, a UhpT homolog which is required for responsiveness to an inducer and activation of UhpB. The existence of a UhpBC signaling complex is suggested by the requirement for UhpC for the activity of certain constitutively active variants of UhpB, the dominance and epistasis relationships of uhp alleles, and the finding that expression of UhpB in excess of UhpC has a strong dominant-negative effect. Expression of a hybrid protein containing the cytoplasmic C-terminal half of UhpB fused to glutathione S-transferase (GST) also interfered with Uhp signaling. This interference phenotype could not result solely from the phosphatase activity of UhpB, because interference affected both overexpressed UhpA and UhpA variants which are active in the absence of phosphorylation. Variant forms of UhpB which were active in the absence of UhpC carried amino acid substitutions near motifs conserved in HK proteins. The GST fusion protein inhibited the ability of UhpA to bind and activate transcription at the uhpT promoter. Unlike the wild-type situation, a GST fusion variant carrying one of the UhpB-activating substitutions, R324C, displayed autokinase activity and phosphate transfer to UhpA but retained the ability to sequester UhpA when it was altered in the conserved residues important for phosphate transfer. Thus, the default state of UhpB is kinase off, and activation of its phosphate transfer activity requires either the action of UhpC or the occurrence of certain mutations in UhpB. The interference phenotype shown by UhpB in excess of UhpC appears to include the binding and sequestration of UhpA.

Bacterial Proteins↗
PubMed1998

Utilisation of transluminal extraction atherectomy in the treatment of saphenous vein graft disease: two case reports.

Saphenous vein graft disease is an increasing problem as more patients undergo bypass grafting and to date the most effective management strategy remains undefined. The major limitations of angioplasty for saphenous vein graft lesions are the risk of distal embolization and restenosis. Primary stenting in this situation results in superior lumen enlargement and higher procedural success but is still associated with significant restenosis. We describe two cases in which transluminal extraction (TEC) atherectomy is utilised for the treatment of vein graft disease with good immediate and long term angiographic results. The first case reports the use of TEC atherectomy for the primary treatment of a discrete eccentric filling defect, and the second case describes the use of this technique in the management of in-stent restenosis.

Adult↗
PubMed1998

The ACC professional life survey: career decisions of women and men in cardiology. A report of the Committee on Women in Cardiology. American College of Cardiology.

OBJECTIVES: This survey was conducted to learn how the career decisions of women and men in cardiology influenced their professional and personal lives. BACKGROUND: Women represent only 5% of practicing adult cardiologists and 10% of trainees. Yet, women and men now enter medical school at nearly equal numbers. The factors that contribute to career satisfaction in cardiology should be identified to permit the development of future strategies to ensure that the best possible candidates are attracted to the profession. METHODS: A questionnaire developed by the Ad Hoc Committee on Women in Cardiology of the American College of Cardiology (ACC) was mailed in March 1996 to all 964 female ACC members and an age-matched sample of 1,199 male members who had completed cardiovascular training. RESULTS: Women were more likely to describe their primary or secondary role as a clinical/noninvasive than invasive cardiologist (p < 0.0001 women vs. men). Men and women both reported a high level of satisfaction with family life, but women were less satisfied with their work as cardiologists (88% vs. 92%, p < 0.01) and with their level of financial compensation. Compared with men, women expressed less overall satisfaction (69% vs. 84%) and more dissatisfaction with their ability to achieve professional goals (21% vs. 9%). These differences were most pronounced for women in academic practice. Women reported greater family responsibilities, which may limit their opportunities for career advancement. Women were more likely to alter training or practice focus to avoid radiation. A majority of women (71%) reported gender discrimination, whereas only 21% of men reported any discrimination, largely due to race, religion or foreign origin. CONCLUSIONS: Women cardiologists report overall lower satisfaction with work and advancement, particularly within academic practice. They report more discrimination, more concerns about radiation and more limitations due to family responsibilities, which may ultimately explain the low percentage of women in cardiology. Attention to these issues may result in programs to improve professional satisfaction and attract the best candidates into cardiology in the future.

Adult↗
PubMed1997

The oblique effect in orientation acuity.

We have examined the dependence of rotational acuity on the orientation bandwidth of a stimulus using two-dimensional, band-pass filtered, spatial noise. Stimuli had a bandwidth of 0.5 octave of spatial frequency, centred at 5.0 cyc/deg, and an orientation bandwidth that covered the range from 0.0 to 25.0 deg. Thresholds were obtained on one principal (vertical), and one oblique axis (45 deg). It was found that acuity declined on both axes as bandwidth increased, in a manner that was compatible with simple statistical principles with virtually perfect sampling of the image. There was some evidence that the intrinsic noise is greater on the oblique axis than on the vertical, and that oblique axes are less densely sampled than the principal axes. These differences are small and are insufficient, either on their own or taken together to explain the oblique effect.

Humans↗
PubMed1997

Subfemtosecond processes in strong laser fields.

Strong field atomic and molecular interactions can be understood by following electronic dynamics inside the laser cycle. This quasistatic perspective introduces the subfemtosecond time scale into strong-field dynamics through time-dependent Born-Oppenheimer surfaces. We discuss both theoretical and experimental results in atomic and molecular ionization and dissociation with applications to femtochemistry. An all-optical Coulomb explosion method for determining time-dependent molecular structure and properties is demonstrated. The concept of time-dependent Born-Oppenheimer surfaces is used to study molecular dissociation and exchange reactions in infrared fields.

Journal Article↗
PubMed1996

Balloon mitral valve dilatation as an aid to weaning from ventilatory support in patients with intractable pulmonary oedema caused by severe mitral stenosis.

Intractable pulmonary oedema in patients undergoing mechanical ventilation must be investigated as older patients with severe mitral stenosis can be rescued by balloon dilatation of the mitral valve, thus enabling elective cardiac surgery at reduced risk. We describe two such cases and discuss the role of transoesophageal echocardiography in the intensive care unit in the diagnosis and management of these patients.

Catheterization↗
PubMed1993

Severity as a key construct in depression.

Mild, moderate, and severely depressed subgroups were operationally defined in a sample of hospitalized patients clinically diagnosed as depressed. Women were overrepresented among the severely depressed patients, but no other demographic differences among subgroups were found. Generalized anxiety and psychic disorganization were significantly more pronounced in patients who were severely depressed. Severely depressed people also reported more role-performance impairments than did those who were less seriously depressed. Among women, a secondary diagnosis of substance abuse was present significantly less often in the severely depressed. Based on self-reports at admission and 4 weeks later, marked improvement was seen only among the moderately depressed. There was not a statistically significant symptom change in the mildly depressed group; for the severely depressed, the change over time was significant but the patients remained highly symptomatic. The authors discuss the importance of the construct of severity for clinical practice, hospital policy, and future research.

Adolescent↗
PubMed1990

A 5-year study comparing a posterior composite resin and an amalgam.

Eighty class I and class II light-cured posterior composite resin restorations were compared with 43 class I and class II amalgam restorations during a 5-year period after placement. The results of this clinical study showed that both materials were satisfactory during the time period and that the only significant statistical differences are a poorer marginal integrity for the amalgam and a greater wear rate for the composite resin.

Adult↗
PubMed1990

Aortic compliance measured by non-invasive Doppler ultrasound: description of a method and its reproducibility.

1. Aortic compliance (expressed as percentage increase in lumen diameter for a pulse pressure of 10 mmHg) was calculated from the characteristic pulse wave velocity deduced from 'foot to foot' transit times of the blood flow pulse over a measured length of aorta. Two continuous wave Doppler ultrasound transducers were used: one insonating the root of the left subclavian artery, the other the abdominal aorta proximal to its bifurcation. Measurements were made after the subject had been supine for 5 min to achieve stable conditions. 2. Transit times were calculated on-line in real-time from the delay between the start of the systolic upstroke in the flow velocity sonograms recorded by the two transducers. 3. Within-visit variation was minimized by measuring over 45 cardiac cycles repeated three separate times and calculating an overall mean value for aortic compliance. A full measurement took 5-10 min. 4. Reproducibility of this overall mean value of aortic compliance was assessed at 1 month in 30 subjects (aged 60 +/- 7 years, mean +/- SD) and at 3 months in 23 different subjects (59 +/- 8 years). Aortic compliance values ranged from 0.1 to 2.0%/10 mmHg. 5. The mean paired difference between aortic compliance values was -0.02 between 0 and 1 months, and 0.03 between 0 and 3 months, with respective 95% confidence limits of -0.06 to 0.03 and -0.03 to 0.09 embracing zero, thus not differing significantly from baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗
PubMed1990

Endocardial pacing through a prosthetic tricuspid valve.

We describe a patient in whom permanent endocardial pacing was accomplished by passage of the electrode through a porcine bioprosthetic tricuspid valve, thereby obviating the need for a second thoracotomy. After 8 years of follow-up, the patient continues to do well with satisfactory pacing and bioprosthetic valve function at the first change of pulse generator.

Bioprosthesis↗